Exercise 37

Human cardiovascular physiology

Cardiac cycle

Concepts to memorize: The two atria contract simultaneously The two ventricles contract

simultaneously Diastole

The relaxation period Systole

The contraction period

Steps of the cardiac cycle

The heart is in diastoleHeart pressure is low

The blood flows passively from the pulmonary and systemic system into the atria

The AV valves open The blood flows into the ventricles The atria contracts to force the residual

blood into the ventricles

Cardiac cycle

The ventricular pressure increases The ventricular systole begins

The atria are in diastole and begin to be filled

The AV valves close The semilunar valves open The blood flows into the aorta and the

pulmonary arteries

Cardiac cycle

The pressure in the aorta and pulmonary arteries increase

The semilunar valves close The ventricles relax

The cardiac sounds (lub-dup pause) First heart sound (S1- lub)

Represents the closing of the AV valves

It happens at the beginning of the systole

Second heart sound (S2- dup)It represents the closing of the

semilunar valvesIt happens at the end of the systole

The cardiac sounds

MurmursIt represents a turbulent blood flowIt is found when blood flows through

narrow openings (stenosis)Also found when there is backflow of

blood (regurgitation) because of defected valves (insufficiency)

Cardiac cycle

Auscultation of the mitral valveOver the 5th intercostal spaceIn line with the middle of the clavicle

Auscultation of the tricuspid valveOver the sternum

Cardiac cycle

Auscultation of the pulmonary valveOver the 2nd intercostal spaceAt left sternal margin

Auscultation of the aortic valveOver the 2nd intercostal spaceAt the right sternal margin

The pulse

It is palpation of the pressure wave that travels along the arteries

The pressure wave causes the expansion of the arterial wall

Parameters detected by the pulse palpation:

Pulse rateIt is the same as the heart rateNormal: 60-100 bpm

The pulse

Pulse rhythm Pulse amplitude Superficial pulse points

Common carotid arteryTemporal arteryFacial arteryBrachial arteryRadial artery

The pulse

Femoral artery Popliteal artery Posterior tibial artery Dorsalis pedis artery

The blood pressure

It is the pressure that the blood causes to the wall of the vessels

It is reported in millimeters of mercury (mm Hg)

Arterial pressure: Systolic pressure

Reflects the pressure in the arteries during ventricular ejection

It is the first readingnormal:120 mm Hg

The blood pressure

Diastolic pressureReflects the pressure in the arteries

during ventricular relaxationIt is the second readingNormal: 80 mm Hg

The blood pressure

Sounds of KorotkoffIndicates the resumption of blood

flow into the forearm when the pressure to occlude the artery is gradually released

First sound heard is the systolic pressure

The disappearance of the Korotkoff indicates the diastolic pressure

The blood pressure

Venous pressure Normal: 30-90 mm Hg They are affected by muscle activity,

deep pressure, breathing, etc

The blood pressure

Pulse Pressure (PP)Systolic pressure – diastolic

pressure Mean arterial pressure (MAP)

MAP=diastolic pressure+PP/3

Effects of various factors on blood pressure

BP=CO * PR Factors that increase PR:

Constriction of arteriesIncreased blood viscosityIncreased blood volumeHardening of the arteries walls

Effects of various factors on blood pressure

Factors that increase BP: Age Weight Drugs Exercise Emotions, etc

Skin color

It indicates local circulatory dynamics Factors that influence skin color

Oxygen supply (cyanosis)Temperature (cold, warm)Hormones (thyroid hormones)Autonomic nervous system

• Fight or flight reaction Collateral blood flow

Electrocardiogram (ECG)

Conduction of impulses through the heart Generation of electrical impulses Detection of the electrical impulses on the body’s

surface Electrocardiograph

The electrocardiogram (ECG)

Deflection wavesThe P wave accompanies the depolarization of

the atria• First wave, small and precedes atrial

contraction

The electrocardiogram (ECG)

The QRS complex appears as the ventricles depolarize• Second wave, large and precedes

ventricular contractionThe T wave indicates ventricular

repolarization; third wave

An Electrocardiogram

The electrocardiogram (ECG)

Intervals- Always include at least one wavePR interval (PQ)

• From the beginning of P wave to the start of QRS

• Represents atrial depolarization and conduction through AV node

QT interval• From the Q wave to the end of T wave• Ventricular depolarization, contraction and

repolarization

The electrocardiogram (ECG)

ST interval• From the end of the QRS to the end of the T

wave• Represents the spread of impulse to the

ventricles (ventricular contraction) + ventricular repolarization

An Electrocardiogram

The electrocardiogram (ECG)

Segments

From the end of one wave to the start of the next one

ST segment• From the end of QRS to the beginning of T

wave• Represents the spread of the impulse to the

ventricles (ventricular contraction)

The electrocardiogram (ECG)

PR segment• From the end of P wave to the beginning of

QRS complex• Represents the spread of the impulse to the

atria (atrial contraction)

An Electrocardiogram

The electrocardiogram (ECG) abnormalities

TachycardiaHR above 100 bpm

BradycardiaHR below 60 bpm

FibrillationUncoordinated heart contractions